Propagate and refine rhododendrons with cuttings and cuttings

Propagation works best in a greenhouse equipped with underfloor heating and additional daylight lamps. However, if you cannot offer these conditions and most plant lovers will be, you can try it without. You shouldn’t let setbacks dissuade you from your goal.

Propagating cuttings is relatively easy, even if a distinction is made between individual groups. There are no major differences between them, just small differences. However, deciduous azaleas only rarely succeed in propagating cuttings. Even professionals have to plan for some failures.

Rhododendrons are also often grafted, simply to make them more adaptable and resilient. The most common way of grafting the plants is through ‘copulation’. Otherwise rhododendrons are propagated through sowing, mossing and lowering. We present all of these species here.

Propagation of cuttings from rhododendrons

The propagation of cuttings is a vegetative propagation, which means that identical descendants come out of it. The new plants have the same properties as the mother plant. In this type of reproduction, rhododendrons are divided into four groups: large-leaved, small-leaved, Japanese azaleas and deciduous azaleas. All four groups differ somewhat in the propagation of cuttings.

Cuttings of large-leaved rhododendrons

• Cut cuttings from mid-July (until mid-September)
• Leaves must already be hardened!
• Always cut on a day that is not warm and sunny!
• Cut early in the morning!
• Cutting length about 10 cm
• Carefully peel off the bottom leaves, leaving only the top 4 to 6 leaves at the end of the shoot.
• Use only budless shoots
• Shorten the leaves on the cutting in half (reduce evaporation area)
• With a sharp and clean knife, cut into the bottom 2 cm at the bottom of the cuttings, as when cutting roses for the flower vase
• Dip the cuttings in rooting powder, then knock them off well
• Put in the substrate (4cm deep) – moist peat or white peat, mixed with some sand, a layer about 15 cm thick
• If several cuttings are placed in a container, keep a planting distance of at least 5 cm
• Moisten the substrate with a fine spray mist
• Cover with transparent film!
• Temperatures at 16 ° C, not higher
• As soon as wound tissue has developed after 2 to 3 weeks, the temperatures can be increased to 20 ° C. No higher temperatures !!!
• No direct sunlight as this increases the temperature too much
• Check weekly for moisture and spray with water if necessary. The substrate should be consistently moist, but never wet !!!
• After 6 to 8 weeks, the cuttings should be rooted

Cuttings of small-leaved rhododendrons

• Cut cuttings from the beginning of July
• Proceed in the same way, but start with a temperature of 13 to 15 ° C
• Under no circumstances higher temperatures
• Only go up to 20 ° C after about 3 weeks, but not higher
• The rooting is usually a little faster in this group

Japanese azaleas cuttings (are treated almost identically and belong to the same group)

• Rooting is usually much easier
• Cut cuttings in August
• Use shoots that are around 10 cm long
• Use only pure white peat as substrate
• Do not use rooting powder!
• Insert 5 cm deep into the substrate
• Cover with foil
• Keep slightly moist evenly
• Rooting usually already after 6 weeks
• Do not isolate or plant immediately until next spring

Cuttings of deciduous azaleas

• Difficult to get rooted, without a greenhouse it is impossible
• Most of the time, the cuttings die off before rooting.
• The propagation should better be left to the specialist here.

Offshoot

Making offshoots is easy. You simply bend a low-growing branch to the ground and bend it a little. At this point of contact, make a small hole in the ground, fill in some peat there and insert the branch. Spread some peat on top and put a stone or a hook on it so that the branch cannot snap up again. It is best to scratch the twig at the kink so that roots can grow out there. Now the earth must always be kept a little moist there. It can take up to a year for roots to form.

• Bend the branch to the ground
• Kink or cut into the contact point
• Put in soil or cover with soil
• Weight down by stone
• Always keep the area slightly moist

Refine rhododendrons

In order to refine a rhododendron, you need a suitable base. Many tree nurseries or professional growers use rootstocks from ‘Cunningsham’s White’ or ‘Roseum Elegans’ because their growth characteristics are better. The plants grow stronger, can cope with non-ideal locations and substrates or tolerate higher pH values. Different finishing methods can be used, for example ‘copulation’, ‘gap plug’ or ‘lateral flattening’. The most common form is ‘copulation’.

• The base and rice must be cut diagonally, but against each other.
• It is important that the shoot is the same thickness as the base so that both parts fit together exactly.
• Then the cut surfaces are placed on top of one another and tied together with special rubber strips.
• Continue to cultivate in breathless air for 2 months

Propagation by sowing

Propagation by sowing is a long story. You can use your own seeds, but you have to be sure that they are germinable seeds. Such seed pods can be recognized by the fact that they are significantly more voluminous than unfertilized ones. The seed pods should be harvested early, as soon as the pistil has dried up, because they then spring up quickly and then the very small seed is lost. In addition, seeds can of course also be purchased.

• It is best to use an indoor greenhouse
• Use a peat substrate mixed with sand and perlite as the cultivation soil
• Sow as quickly as possible, fresh seeds germinate best.
• Place the greenhouse in a light, but not sunny and warm place
• Pay attention to constant, but only slight, moisture.
• Seedlings should show up after about 6 weeks.

• The seedlings can only be pricked out after a year.
• Only then are they allowed to get some fertilizer.
• The first flower buds usually appear after three years. Sometimes it takes longer.

Measure rhododendron

When mossing, a single variety duplicate of the mother plant is created, i.e. a clone with the same properties and the same appearance. Mossing also requires a little patience.

• An incision is made at an upward branch end from the previous year.
• The cut must not be so deep that there is a risk of the branch breaking off.
• The incision is spread open a little and some spaghnum moss is clamped into it to keep it open.
• Then the still moist spaghnum is wrapped generously around the cut, so that a mass about the size of a fist is created.
• A cuff is wrapped around it from black plastic film.
• This is attached to the branch with a thin wire at the top and bottom.
• After one to two years, roots should have sprouted from the interface and rooted through the spaghnum ball.
• If so, the branch can be cut off and potted separately.
• Do not plant out until the following year!

Frequently asked questions

Why is it that colored rhododendrons suddenly only bloom white?
Since the original variety has prevailed and sprouted. This is a refined specimen that was refined on a mostly white blooming base. The rootstock has sprouted heavily and displaced the noble rice. Usually only one or two shoots of a different color initially bloom. If you don’t remove this, the pad keeps drifting on. At some point the entire plant will only bloom white.

Why are some varieties of rhododendron so expensive. It is not uncommon for a plant of normal retail size to cost a few hundred euros?
I couldn’t find out the exact reason. I just think that some strains are very new and therefore not widely used yet. The less they are offered, the more expensive they will be. In addition, some varieties and cultivars are also protected, which in turn makes them more expensive to sell. But why such high prices come about is not clear. However, there are collectors of many plant species and therefore horrendous prices. Just think of peonies or daylilies, there are also prices of several hundred euros, although the normal varieties only cost 5 euros. Supply and demand regulate the prices and there are also normal varieties at moderate prices.